Geeky Medics guide to writing Single Best Answer (SBA) Questions

Most undergraduate and postgraduate medical examinations of knowledge now use the single best answer (SBA) format. Here at Geeky Medics, with your help, we hope to grow a question bank of relevant, contemporary and challenging questions that follow this common format.

The following is a brief and simple guide to creating questions for our collection.

General points

Use clear and precise language. Avoid question ambiguity. This way only knowledge and application of knowledge is tested.

We are not currently using images in our questions, so ensure your question does not require imagery for it to make sense.

Question structure and content

Max 150 words

Present tense

Avoid superfluous information

Avoid abbreviations

Structure the contents of the question stem as follows (including only information relevant to the question):

Patient details (gender/age)

Presenting complaint (PC)

History of presenting complaint (HPC)

Relevant past medical history, family history and social history

Observations/Vitals /GCS/MMSE

Physical examination findings

Results (e.g. laboratory / radiology)

Ask for a BEST answer, NOT one that is TRUE/FALSE, for example…

‘What is the MOST likely diagnosis?’

‘What is the BEST initial management step?’

‘What is the MOST common X-ray finding?’

Avoid negative questions (e.g. ‘What is the LEAST likely diagnosis’)

Check your question passes the “best practice cover test” – the candidate should be able to answer the question solely from the stem of the question, with the answers covered.

The answers

Keep them short

You should provide 5 possible answers

They should flow grammatically from the question stem

They should be homogenous (e.g. they should all be a diagnosis/treatment/anatomical location etc)

Avoid having multiple variables in the same answer (e.g. give oxygen AND morphine)

All should be plausible and familiar, but one should be BETTER than the others

The BEST answer is evidence-based and widely agreed upon by experts (e.g. NICE guidelines)

List the answers in alphabetical or numerical order (this removes any bias as to where you’ve placed the “correct answer”)

The explanation

The explanation should first identify the correct answer. It should then expand on why a particular answer is more correct than the other options, demonstrating to the candidate the reasoning behind the selection. The explanation should then move on to discuss why the other possible answers were less correct in some more detail. You should provide enough information to explain the answer and provide some key learning points (but not overload the candidate with superfluous information that dilutes the core explanation of the question). To provide more in-depth information and context you should provide a further reading link to a reputable resource (e.g. relevant guideline). Avoid linking to resources that require a membership or payment to access.

Example of a good question

Question

Sandy Hughes, 67, presents to A&E with chest pain. She describes 12 hours of a sharp chest discomfort on inspiration, which started suddenly just after she arrived back from her flight to Florida. Her oxygen saturation is 94% on 2 litres of oxygen and her respiratory rate is 28. What is the most likely ECG finding for this patient?

Answers

A) Right axis deviation

B) SI QIII TIII pattern

C) Sinus tachycardia

D) ST elevation in three contiguous leads

E) Widespread saddle-shaped ST elevation

Explanation

The most likely ECG finding in this patient is sinus tachycardia.

This patient has presented with the classic signs of a pulmonary embolism (PE)– recent travel, sudden onset chest pain which is worse on inspiration, and increased respiratory rate with low oxygen saturations. ECG findings in PE can include right axis deviation, sinus tachycardia, and the oft-mentioned but rarely seen SI QIII TIII pattern. Of these, the most likely is a sinus tachycardia.

ST elevation in three contiguous leads would be seen in an ST-elevation myocardial infarction rather than a PE, and widespread saddle-shaped ST elevation is indicative of pericarditis.

What makes this a good question?

The information in the stem is relevant and is written in a clear manner. This is a two-step question which is slightly more challenging- the reader must first choose a likely diagnosis for the patient, and then consider subsequent ECG findings. None of the answers are ‘wrong’– all could be seen in a patient with chest pain. However, the best candidate would rule out findings not seen in PE and then choose (as the question asks) the most likely ECG finding. The explanation is informative and explains which of the answers are more or leastlikely, and why. The answer is also referenced for further information.

Examples of some bad questions

Example 1

Question

A male patient presents to his GP with a cough. The patient describes feeling unwell. They have a past medical history of an appendectomy. What is the most likely diagnosis?

A) COPD

B) Hypersensitivity pneumonitis

C) Lung cancer

D) Pneumonia

E) Tuberculosis

Answer

The correct answer is pneumonia, as it is statistically the most likely diagnosis in a patient presenting to their GP with a cough.

Why is this a poor quality question?

The stem is vague – in order to correctly answer the question, the reader would need more details such as the patient’s age, related symptoms, smoking history, occupational history, travel history, etc. The past medical history of an appendectomy is entirely irrelevant to the stem.

The patient could have any of the above conditions – all may present with a cough and “feeling unwell”. Of course, statistically speaking, pneumonia is likely the most common diagnosis made in someone presenting to their GP with a cough. However, this question isn’t testing any diagnostic skills in the reader. Questions should be asking what the most likely diagnosis is in a patient given the information and background provided.

Example 1 reworked

A male patient, aged 73, presents to his GP with a six-week history of a cough. The patient also describes feeling ‘run down’ lately and has lost weight. He has on occasion coughed up some blood. The patient has a smoking history of 80 pack-years.

What is the most likely diagnosis?

A) COPD

B) Hypersensitivity pneumonitis

C) Lung cancer

D) Pneumonia

E) Tuberculosis

Answer

The most likely diagnosis in this patient is lung cancer.

All of the above conditions could present with a cough, however only tuberculosis and lung cancer are likely to present with haemoptysis and weight loss as well. The patient’s smoking history, combined with no known history of fevers or other risk factors, makes lung cancer the most likely diagnosis in this patient.

Further information on differentials of a chronic cough: http://bestpractice.bmj.com/best-practice/monograph/69/diagnosis/differential-diagnosis.html

Example 2

Question

Which joint disease is associated with morning stiffness that improves with activity?

A) Ankylosing spondylitis

B) Gout

C) Osteoarthritis

D) Rheumatoid arthritis

Why is this a poor quality question?

It is in a multiple choice rather than single best answer format. There is no clinical vignette or background information, and there are only four options for answers rather than five. Additionally, morning stiffness is seen in both rheumatoid arthritis and ankylosing spondylitis.

Example 2 reworked

Alice McAvey, 51, has presented to rheumatology outpatients with pain in her hands. She describes five weeks of pain and stiffness in her joints in the morning, lasting around 30 minutes. Her pain often improves with some light activity.

What is the most likely diagnosis in this patient?

A) Ankylosing spondylitis

B) Gout

C) Osteoarthritis

D) Psoriatic arthritis

E) Rheumatoid arthritis

Answer

The correct answer is rheumatoid arthritis.

All of the above conditions cause joint pain, however only ankylosing spondylitis, psoriatic arthritis, and rheumatoid arthritis are associated with morning stiffness. Ankylosing spondylitis is known to affect the spine, not the hands. Given that there is no known history of psoriasis in this patient, rheumatoid arthritis is the most likely answer.

Gout and osteoarthritis are less likely to be symmetrical in presentation, and would not present with morning stiffness.

Further information: http://bestpractice.bmj.com/best-practice/monograph/1191/diagnosis/differential-diagnosis.html

Note that this question is still testing the same knowledge as the original!